AIBU to want to tell sibling I’m going no contact?

Maybe not. But it doesn't sound like the youngest sibling has done anything horrific enough to deserve what eldest sibling has done 'to' her.

Hence, even as the imperfect possibly-also-in-the-wrong middle sibling - I'd still be airing my thoughts to eldest sibling (after the wedding).

I have no idea why so many people are jumping to the defence of the older sibling here

I don't think there's too many people defending the sister here. There are several pointing out that the OP isn't showing impeccable behaviour here either.

you sound…. odd

I think I can live with that.

I have no idea why so many people are jumping to the defence of the older sibling here...that's what I view as odd tbh. It's an awful, awful thing to do to your younger sister with no notice. Totally inexcusable behaviour.

Maybe oldest sibling and family decided to go abroad because they've had an exceptionally tough time recently, could tell that their two siblings were against them and couldn't cope with any potential toxicity at the wedding. IE it was an act of self protection for themselves, not a move calculated to hurt their two siblings

Oh give over. NO ONE remotely reasonable does this...just flies off abroad 3 days before a wedding without a word. Not even telling their sibling they now have X members of their actual wedding party missing. It's incredibly spiteful and the only possible motivation I can see would be to create drama and as much disruption as possible. If it was an act of self protection and literally impossible for their MH to attend they could still have let them know, via their parents - any decent person would IMO.

Op I'm sure there are probably more sensible/less aggravating options but you've asked for opinions so here's what I'd do if it was one of my sisters...

Say nothing now. Don't bitch or moan, don't even hint at being upset with elder sibling. Be there for your younger sibling. Console, reassure, be practical, help as much as possible. Paste a smile on your face and deflect from any mention of elder sibling your parents make. Not one bad word. Be the peacemaker, do everything in your power to ensure the wedding runs as smoothly as possible and that siblings actions don't spoil the day.

When your sister's back in the UK and the wedding is done, I'd go visit her. And I'd tell her to her face what a spiteful, vicious, selfish, jealous bitch she was. I'd tell her that she's the gossip of the moment and you lost count of the people at the wedding who expressed their disgust with her and her actions. Then I'd tell her never to contact me again and that I never wanted to lay eyes on her hateful face again.

I would absolutely go NC over this, it's unforgivable imo. And I would never be able to take the moral highground entirely, if it was one of my sisters I would absolutely make sure she 100% knew my thoughts.

Gosh, I sympathised you until the update about your siblings loss. I really think you need to read that back… those paragraphs do not show you in good light.

Aaaaand, you’ve somehow made it even worse.

You really think they “announced” their miscarriage because you had your parents attention?! I think you need to look closer to home.

I wouldn't be able to say nothing. I wouldn't "announce" that I'm going no contact but I would phone them or message them and say that to pull out of your siblings wedding and leave the country is completely unforgivable and they should seriously reconsider if they want a relationship with you or your younger sibling going forward. Your parents also need to be told how unfair they are being.

Yes. It's interesting to me how OP is interpreting every action taken by oldest sibling as being all about 'attacking' OP and youngest sibling.

Maybe oldest sibling and family decided to go abroad because they've had an exceptionally tough time recently, could tell that their two siblings were against them and couldn't cope with any potential toxicity at the wedding.

IE it was an act of self protection for themselves, not a move calculated to hurt their two siblings.

approx 1 week before my due date last year with my first baby they announced they had a miscarriage (no one knew they were pregnant),

I can’t be bothered to type what I was going to before this.

You CBA to read, but you feel you should take a moment for a sarky reply?

Interesting choice.

I was with you until this:

approx 1 week before my due date last year with my first baby they announced they had a miscarriage (no one knew they were pregnant)

I am sure, no matter how vindictive you think your older sibling is, that they didn’t miscarry their baby to steal the thunder from you having yours. It’s absolutely unbelievable that you think your sister should have kept their miscarriage a secret because you were having a baby. I think the fact that you’ve mentioned that shows who you are and probably explains why your parents side with your older sibling.

The Op has presented it as a Cinderella story of the spoilt favoured older one and the lovely hardworking younger pair

In one of OP's replies I note that the parents were working a lot and 'put the oldest in charge of the younger two'.

it sounds like the oldest was parentified at potentially quite an early age and this too can cause damage and resentment.

As you say, the other side would be interesting especially as it sounds like the oldest and their family is currently really going through it.

I agree with your husband. Don't say anything, but equally there is no reason to contact or visit your elder sibling. Over time, they will just disappear from your life.

Going NC is a big, big deal. It is life-altering. It should only ever be used as an absolute last resort as it will have long-tern consequences, not only for the sibling you go NC with but for your relationships with your whole family.

Here are some questions to ponder which you may find helpful whilst you come to a decision:

1. Am I prepared never ever to speak with my sibling ever again, even if my feelings towards them change? Even if I need them one day?
2. Am I going NC to protect myself or to show solidarity with my sibling?
3. Is it genuinely my desire to go NC, or do I just want to let my sibling know how angry I am, and am using the threat of NC as a weapon to 'prove' how angry I am?
4. How would I feel if my youngest sibling's relationship with the oldest dramatically improved in years to come, and they became close? Would I be happy to still be on the outside?
5. How would I feel if my going NC caused anguish and pain to my parents? How will I explain it to them if they express their anguish to me?
6. In a hypothetical situation whereby one of my parents, close to death, begs me to reconcile with my sibling, will I still be confident in explaining and sticking to my NC, even at the risk of breaking my parent's heart?
7. Am I sure in myself that going NC is to protect myself and not out of feelings of jealousy or resentment that the oldest sibling appears to be the favoured one?
8. What will be the plan for future family gatherings, since I and my NC-sibling cannot be in the same place at the same time? Who will broker a fair arrangement by which we take family gatherings in turn?
9. When my parents pass away, who will be the family member who will broker communications with my sibling and me, since we will not be speaking? What if we are joint executors?
10. What will I tell my children, should they ever want to meet their aunt/uncle?
11. Finally, can I accept that if I tell my sibling I'm going NC, they may also have long held (and in their view justified) resentments they want to communicate to me? Am I ready to hear and respond to these?

If you're confident you're prepared/have firm answers to all these questions, you're ready to go NC. Good luck. It is heart-breaking, but sometimes necessary for self-protection.